[英]fetch all records using PagingAndSortingRepository in spring-data-jpa
[英]JOIN FETCH in spring-data-jpa does not fetch lazy associations
我在spring-data-jpa
获取懒惰的@ManyToMany
关联时遇到问题。 我有一个电影列表,该电影列表与使该电影成为最爱的用户和类型列表相关联:
@Entity
@Table("movie")
public class Movie {
...
@ManyToMany(fetch = FetchType.EAGER)
@JoinTable(...)
private List<Genre> genres;
@ManyToMany
@JoinTable(name = "users_movies",
joinColumns = @JoinColumn(name = "movie_id", referencedColumnName = "id"),
inverseJoinColumns = @JoinColumn(name = "user_id", referencedColumnName = "id"))
private List<User> users = new ArrayList<>;
}
类型也与已将此类型标记为收藏的用户相关联:
@Entity
@Table("genre")
public class Genre {
....
@ManyToMany
@JoinTable(name = "users_genres",
joinColumns = @JoinColumn(name = "genre_id", referencedColumnName = "id"),
inverseJoinColumns = @JoinColumn(name = "user_id", referencedColumnName = "id"))
private List<User> users;
}
而且我有一个存储库,其中包含以下方法/查询,该存储库必须按喜欢的流派返回所有电影,并加载电影的用户,以便可以显示用户是否将该电影标记为喜欢的电影:
@Query(value = "SELECT movie FROM Movie movie " +
"JOIN movie.genres genre JOIN genre.users grenreUser " +
"LEFT JOIN FETCH movie.users " +
"WHERE grenreUser.id = :userId",
countQuery = "SELECT COUNT(movie) FROM Movie movie " +
"JOIN movie.genres genre JOIN genre.users grenreUser " +
"LEFT JOIN movie.users " +
"WHERE grenreUser.id = :userId")
Page<Movie> getAllMoviesByFavoriteGenres(@Param("userId") String userId, Pageable);
但是这里我有一个问题,执行此查询后, movie.getUsers()
为空。
我发现使用@EntityGraph
可以有所帮助,但movie.getUsers()
关联仍然为空。
我也尝试为了进行测试而将此关联设置为FetchType.EAGER
,但它仍然为空。
我没有主意,所以我将不胜感激。
UPD:这可能不是数据库中不存在用户的问题,因为我有另一个查询,该查询仅提取在“收藏夹”用户流派中被用户标记为“收藏夹”的电影。 因此,如果数据库中不存在该用户,则查询将返回空结果,但即使movie.getUsers()
为空,我也可以获得结果。 这是方法/查询:
@Query(value = "SELECT movie FROM Movie movie " +
"JOIN movie.genres genre " +
"JOIN FETCH movie.users user " +
"WHERE user.id = :userId AND :userId MEMBER OF genre.users",
countQuery = "*same but with count*")
Page<Movie> getAllFavoriteMoviesByFavoriteGenres(@Param("userId") String userId, Pageable);
是的,单向映射应该起作用。 对于您正在做的基本示例,我没有任何问题。 这应该是一个很好的起点,可以帮助您找出差异。 我注意到,我不加入movie.users
在countQuery
。
@Entity
public class Movie {
@Id @GeneratedValue private Long id;
@ManyToMany
private Set<Genre> genres;
@ManyToMany
private Set<User> users;
@Entity
public class Genre {
@Id @GeneratedValue private Long id;
@ManyToMany
private Set<User> users;
@Entity
public class User {
@Id @GeneratedValue private Long id;
和存储库:
public interface MovieRepository extends JpaRepository<Movie, Long> {
@Query(value = "SELECT movie FROM Movie movie " +
"JOIN movie.genres genres JOIN genres.users users LEFT JOIN FETCH movie.users " +
"WHERE users.id = :userId",
countQuery = "SELECT COUNT(movie) FROM Movie movie " +
"JOIN movie.genres genres JOIN genres.users users " +
"WHERE users.id = :userId")
Page<Movie> getAllMoviesByFavoriteGenres(@Param("userId") Long userId, Pageable page);
并使用它:
@Override
public void run(String... args) throws Exception {
create();
System.out.println("something");
Page<Movie> movies = movieRepo.getAllMoviesByFavoriteGenres(1L, PageRequest.of(0, 10));
movies.forEach(System.out::println);
}
private void create() {
User u1 = new User();
userRepo.save(u1);
Set<User> users = Collections.singleton(u1);
Genre g1 = new Genre();
g1.setUsers(users);
genreRepo.save(g1);
Set<Genre> genres = Collections.singleton(g1);
Movie m1 = new Movie();
m1.setGenres(genres);
m1.setUsers(users);
movieRepo.save(m1);
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.